feat: transaction implement

internal/transaction/state.go

@@ -0,0 +1,79 @@
+package transaction
+
+import "fmt"
+
+// State 是服务端更新事务的持久化状态。
+type State string
+
+const (
+	StateCreated     State = "CREATED"
+	StateValidating  State = "VALIDATING"
+	StatePrepared    State = "PREPARED"
+	StateStarting    State = "STARTING"
+	StateSwitching   State = "SWITCHING"
+	StateVerifying   State = "VERIFYING"
+	StateDraining    State = "DRAINING"
+	StateCommitted   State = "COMMITTED"
+	StateRollingBack State = "ROLLING_BACK"
+	StateRolledBack  State = "ROLLED_BACK"
+	StateFailed      State = "FAILED"
+)
+
+var forwardTransitions = map[State]State{
+	StateCreated:    StateValidating,
+	StateValidating: StatePrepared,
+	StatePrepared:   StateStarting,
+	StateStarting:   StateSwitching,
+	StateSwitching:  StateVerifying,
+	StateVerifying:  StateDraining,
+	StateDraining:   StateCommitted,
+}
+
+// Valid 报告状态是否属于当前状态机协议。
+func (s State) Valid() bool {
+	switch s {
+	case StateCreated,
+		StateValidating,
+		StatePrepared,
+		StateStarting,
+		StateSwitching,
+		StateVerifying,
+		StateDraining,
+		StateCommitted,
+		StateRollingBack,
+		StateRolledBack,
+		StateFailed:
+		return true
+	default:
+		return false
+	}
+}
+
+// Terminal 报告事务是否已经不可再推进。
+func (s State) Terminal() bool {
+	return s == StateCommitted || s == StateRolledBack || s == StateFailed
+}
+
+// CanTransitionTo 校验正常推进、回滚和不可恢复失败三类转换。
+func (s State) CanTransitionTo(next State) bool {
+	if !s.Valid() || !next.Valid() || s.Terminal() {
+		return false
+	}
+	if s == StateRollingBack {
+		return next == StateRolledBack || next == StateFailed
+	}
+	if next == StateRollingBack || next == StateFailed {
+		return true
+	}
+	return forwardTransitions[s] == next
+}
+
+// TransitionError 表示状态机拒绝了一次转换。
+type TransitionError struct {
+	From State
+	To   State
+}
+
+func (e *TransitionError) Error() string {
+	return fmt.Sprintf("transaction state transition is not allowed: %s -> %s", e.From, e.To)
+}